Heat half the oil in a large pan or dish with a lid over a medium-high heat, and fry the meat for 5 mins until browned. Remove from the pan and set aside.
Add the remaining oil to the pan and tip in the veg and pancetta. Cook for 10 mins until the onion has softened. Turn up the heat and cook for 3 more mins or until the pancetta begins to brown. Add the beef back to the pan. Pour in the wine and bring to the boil, cooking until the liquid has reduced by half. Tip in the tomatoes, purée, stock, herbs and sugar. Lower the heat and season to taste. Place a lid on the pan and cook over a low heat on a gentle simmer for 2-2½ hrs until the meat is tender. Once cooked, shred the meat into smaller chunks with two forks and stir everything together. Check again for seasoning.
Heat the oven to 200C/180C fan/gas 6. To make the white sauce, heat the butter in a saucepan until foaming. Stir through the flour and cook for 2 mins. Gradually whisk in the milk until smooth. Return to the heat and simmer for 5 mins until thickened, whisking continuously. Stir through the cheese, nutmeg and season.
Tip a thin layer of meat sauce into a 25 x 30cm sized dish, followed by a layer of lasagne sheets, then a layer of the meat sauce, followed by a drizzle of the white sauce. Repeat until all the pasta and meat sauce have been used, then finish with a layer of pasta sheets topped with a thick layer of white sauce. Sprinkle over the parmesan and mozzarella.
Bake for 1 hr until golden and bubbling. Check halfway through cooking – if it is already browned, cover with foil. Serve with a punchy, dressed green salad, if you like.